The present invention relates to a method of and an apparatus for a biofeedback feedback for individual co-ordination of physical factors applied to a subject for treatment purposes among other applications with physiological parameters of the subject.
Continued metabolism is the common denominator of life. Biological systems require energy for continual metabolism, functioning and restoration. Normal cellular metabolism provides energy and homeostatic heat for nominal biological system function. The study of many biological objects proves that cellular metabolism and almost all homeostatic processes are oscillating, and the oscillations are determined by the state of system itself/Malik M., Heart Rate Variability, NY, 1995; Friedman H., Lubart R., Proc. SPIE, Vol.2630, pp.60-64, 1996/The oscillations are driven by complex of mechanisms having non-linear nature and are reflected by time-varying properties such as intermittent synchronization/Mainardi L. T. et all, IEEE Engineering in Medicine and Biology, Vol.16,No 6, pp.64-75, 1997/That means that metabolic and homeostatic oscillations do not interfere or summarize, and they are synchronized/Landa P. S. and Rosenblum M. G., Priroda, No 8,pp.18-27,1992/. Intermittent coupling in normal function of biological systems is displayed by a dynamic hierarchy of biological rhythms that continuously vary in time. The struggle between the time-domain processes of separate mechanisms on the one hand to persist in their intrinsic behavior and, on the other hand, to pursue the coordinated by non-linear mechanisms time-domain rhythm leads to a phenomenon known as a dynamic chaos/West A. J., Fractal Physiology and Chaos in Medicine, NY, 1990/.
Injury and disease cause disturbances of different physiological rhythms and alter the general structure of dynamic chaos. The key of such chaotic behavior of biological systems lies in a fact that they have extreme sensitivity to the temporal behavior of a perturbing factor acting simultaneously on several homeostatic levels/Olsen L, F. and Degn H., Rev. of Biophysics, Vol.10, No 2, pp163-225, 1985/Oscillations of such factor not being coordinated with the temporal dynamics of metabolic and homeostatic processes may effect at the moments when their energetic requirements may not be able to maintain. As a result, it initiates unspecific reaction of an organism directed either to restoring the initial state or to transformation in a new unpredictable state. Physical action such as ultrasound, electromagnetic waves, laser and X-ray radiation simultaneously effect several homeostatic levels of a biological system and not being coordinated with their temporal dynamics have low predictability of the treatment effect. Besides, predetermined doses that usually are used in physical, laser and radiotherapy are far from individual, and that markedly decreases the treatment effectiveness.
The biofeedback methods and systems for co-ordination an individual's physiologic functioning and applied physical action are well known in the art. Conventional biofeedback techniques can be classified in two groups. The first one involves a mental modifying of an individual's physiological functioning by providing "feed-back" of their physiological activities. Known instruments of this category provide indication of the heart rate/U.S. Pat. No. 4,450,843 issued May 29, 1984 to Barney et all; U.S. Pat. No. 5,007,430 issued Apr. 16, 1991/, brain waves/U.S. Pat. No. 4,031,884 issued Jun. 28, 1977 to Henzel et al/, blood pulse waves/U.S. Pat No. 4,450,843 to Barney et all; U.S. Pat. No. 5,475,725 issued Dec. 12, 1995 to Nakamura et al/. Biofeedback methods and systems of other type in this group convert measurable physiological activities of an individual into feedback signals comprising an auditory or visual stimulus/U.S. Pat No. 4,883,067 issued November 1989 to Knispel et al/.
These feedback techniques have well known limitations. The feedback signal normally indicates only a time average of the relevant physiological activity and has no direct effect on ongoing biological processes involved in a disease and, therefore, can not produce a true real time feedback control. Further, the pathway by which feedback signals control an individual's physiological functioning includes such low predictable parameter as emotional state of the individual. Besides, the success of the treatment sufficiently depends on education and professional skills of the instructor that learn the individual how to control physiological function.
Biofeedback techniques of second group have opposite direction of controlling and control the factor applied to the individual being treated. Various patents disclose these instruments. Most of them directly control the factors effecting only one ongoing process involved in a disease. U.S. Pat. No. 5,522,854 issued Jun. 4, 1996 to Ideker et al discloses a method and apparatus for biofeedback stimulating an implanted electrostimulator. Provided by monitoring the symphatetic and parasymphatetic nerve activity biosignals are processed to produce treatment through electric shock at the moments of detection of the states of high risk arrhythmia. Similar biofeedback system delivering electrical stimuli directly to cardiac tissue is disclosed in U.S. Pat. No. 5,447,520 issued Sep. 5, 1995 to Spano et al. According to this invention the timing of intervals between heart beat pulsation in response to a single stimulus intervention is performed during approximately 5 to 60 seconds. At this time the dynamic behavior of a chaotic regime is evaluated according to a special algorithm. At high risk moments of arrhythmia determined by this algorithm biofeedback signals control tissue stimulus injector.
An important advantage of these inventions is that they produce feedback signals in a real time. However, their application is limited by sensitivity to only one level of cardiac control, and controlling is provided only after a cardiac event has already occurred. Much more wider sensing or therapeutic vigilance with progressively higher degrees of therapy is disclosed by U.S. Pat. No. 5,749,900 issued May 12, 1998 to Schroeppel et al. The feedback signals are derived from comparison of evaluated numbers of the heart rate variability with previously stored one, and according therapy regimes are initiated.
All above described techniques related to the second group provide control of the physical factor effecting only one physiologic parameter, which is monitored. Being used for controlling the action of multilevel action in physical, laser and radiotherapy these techniques do not provide synchronization of the action simultaneously with several homeostatic levels of an organism and, therefore, cannot enhance reproducibility of the treatment effect and effectiveness of the treatment. Perhaps the only one feedback system, which is able to synchronize physical factor of multilevel action is disclosed by USSR Patent 1,481,920 issued Nov. 14, 1986 to Zaguskin et all. According to the patent the cell biorhythms are determined at the first step. Then the physical action applied to the biological object is modulated by at least three frequencies selected from a measured cell rhythm spectrum. It is believed that synchronization of the factor with several frequencies of the cell rhythm is adequate to synchronization to rhythms of all homeostatic processes. Not dealing with biological aspect of this method it should be just mentioned that measurement of the cell rhythms in vitro principally prevents biofeedback control in a real time.
In view of the foregoing, there has been no biofeedback method or apparatus for synchronization of the physical factor applied to a subject for treatment purposes with biological rhythms of several homeostatic processes simultaneously.
It is believed that co-ordination of the interaction between homeostatic rhythms and their intermittent synchronization is reflected in peripheral blood pulse circulation/Goldberger A. L. and West B. J., Fractals in Physiology and Medicine, Yale J. of Biology and Medicine, Vol.60,pp421-435, 1987./Being a multisystem blood supplies oxygen and nutrients and clear metabolic waste products. A complex neural and neuro-hormonal mechanisms controlled by Central and Autonomic Nervous Systems co-ordinate the peripheral blood flow with rhythms of metabolic and homeostatic processes/Bayevsky R. M., Prognosis of Boundary States between Norm and Pathology, Medicine, Moscow, 1979./Thus, blood flow through the body is adjusted to the momentary harmony of biological rhythms by combination of regional and higher level control mechanisms, and any factor, which is synchronized with blood flow will be co-ordinate to it too. Unfortunately, there has been no biofeedback technique available for synchronization the factor applied to a subject with cycles of its peripheral blood flow.
Usually these cycles are derived from a pulsatile component (a.c.) of the photoplethysmographic (PPG) signal sensing from a subject. Along with a small a.c. component attributable to light attenuation changes resulting from blood volume changes during cardiac cycle the PPG signal contains a large nonpulsatile component (d.c.) regarded to light attenuation produced by fixed elements in the tissue. Because the d.c. component does not contain information about blood flow it has to be removed of the signal. In conventional biofeedback technique the d.c. component is subtracted by blocking with a capacitive blocking element. Such elimination of the d.c. component cause--strong distortion of the remaining a.c. component and the distortion depends on the a.c. amplitude variations. Thus, the distortion varies from a subject to subject and even from pulse to pulse. That makes locating the points of discrimination between different cycles in pulse wave of blood flow very hard.
Conventional pulse oxymeters are also used for the PPG signal and for locating the discriminating points/Design of Pulse Oximeters, Edited by J. G. Webster, Publ. By Institute of Physics Publishing, Bristol and Philadelphia, 1997L The signal for calculation of the blood oxygen saturation is derived from the same pulse wave. Along with removing me d.c. component of the signal by blocking/U.S. Pat. No. 4,305,401 issued Dec. 15, 1981 to M. Reissmueller et al/the U.S. Pat. No. 4,800,495 issued Jan. 24, 1989 to R. Smith discloses the pulse oxymeter with programmable elimination of the d.c. component by offset amplifier that offsets a portion of the d.c. component of the PPG signal. To achieve utilization of entire dynamic range of the current-to-voltage converter this pulse employs a complex procedure of signal digital construction-reconstruction. The primary problem of such elimination is that it leaves the a.c. pulsatile component centered not enough close to zero level. That makes it hard to identify the discriminating points in pulse wave. This problem remains also when elimination is performed accordingly by the U.S. Pat. No. 4,086,915 issued May 2, 1978 to Kofsky et. al.